1. Field of Invention
The invention relates generally to an activation control unit and a control method thereof for an occupant protection apparatus. More specifically, the invention relates to a preferred activation control unit and a control method thereof for an occupant protection apparatus that activates the occupant protection apparatus in order to protect an occupant when a vehicle is involved in a collision.
2. Description of Related Art
One example of related art is an activation control unit for an occupant protection apparatus such as that disclosed in Japanese Patent Application Laid-Open Publication No. 10-152014. This unit includes a floor sensor provided in a center portion in the vehicle body, for outputting a signal indicative of an impact received by a vehicle body during a collision. When a parameter based on the output signal from that floor sensor exceeds a threshold value, the unit deploys an airbag which serves as an occupant protection apparatus. This unit also includes a front sensor provided on a front portion of the vehicle body, for detecting a signal indicative of the impact received by that portion of the vehicle body. The unit changes the threshold value to a small value when the impact received by the front portion of the vehicle body in a collision, which is indicated by the output signal from the front sensor, becomes equal to, or greater than, a reference value. This construction facilitates deployment of the airbag when a large impact is received by the front portion of the vehicle body during a collision. Therefore, with this unit, it is possible to appropriately activate the airbag apparatus in order to protect an occupant in a collision in which the airbag should be deployed even when there is not a lot of impact on the center portion of the vehicle body.
Depending on the type of collision, even if there is not a lot of impact on the center portion of the vehicle body, there are cases in which it is necessary that the airbag deploy if the impact on the front portion of the vehicle body is large. Conversely, as well, there are also cases in which, even if the front portion of the vehicle body receives a large impact, it is not necessary that the airbag deploy. However, in the aforementioned unit, because the threshold value for activating the airbag apparatus is always changed to a small value when an impact on the front portion of the vehicle body during a collision is equal to, or greater than, a reference value, it is possible that the airbag might deploy accidentally. Therefore, in deploying the airbag apparatus appropriately according to the type of collision, it is not always appropriate to change the threshold value for activating the airbag apparatus when the impact on the front portion of the vehicle body during a collision is equal to, or greater than, the reference value, as with the aforementioned unit.